Looking West over the I-580 freeway as it snakes through the Livermore Valley on Wednesday July 11, 2012, as seen from the Airway Blvd. overpass in Livemore, Calif. The Bay Area Air Quality Management District has called for another Spare the Air day for tomorrow Thursday July 12. less

Looking West over the I-580 freeway as it snakes through the Livermore Valley on Wednesday July 11, 2012, as seen from the Airway Blvd. overpass in Livemore, Calif. The Bay Area Air Quality Management District ... more

The Valero refinery in Bencia,Ca., as seen on Tuesday June 20, 2017. The Bay Area Air Quality Management District on Wednesday is expected to approve the nation's first limits on greenhouse gas emissions from oil refineries. less

The Valero refinery in Bencia,Ca., as seen on Tuesday June 20, 2017. The Bay Area Air Quality Management District on Wednesday is expected to approve the nation's first limits on greenhouse gas emissions from ... more

The Phillips 66 refinery in Rodeo Ca., as seen on Tuesday June 20, 2017. The Bay Area Air Quality Management District on Wednesday is expected to approve the nation's first limits on greenhouse gas emissions from oil refineries. less

The Phillips 66 refinery in Rodeo Ca., as seen on Tuesday June 20, 2017. The Bay Area Air Quality Management District on Wednesday is expected to approve the nation's first limits on greenhouse gas emissions ... more

Downtown office buildings are barely visible through the haze in Oakland, Calif. on Tuesday, Jan. 7, 2014. The Bay Area Air Quality Management District issued a Spare the Air Alert for Monday, May 22, 2017.

Downtown office buildings are barely visible through the haze in Oakland, Calif. on Tuesday, Jan. 7, 2014. The Bay Area Air Quality Management District issued a Spare the Air Alert for Monday, May 22, 2017.

Photo: Paul Chinn / The Chronicle / /

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Here are the grades given to the Bay Area counties (including San Joaquin county) for particle pollution.

San Joaquin — F

Here are the grades given to the Bay Area counties (including San Joaquin county) for particle pollution.

Smoke from the Southern California wildfires in the Bay Area triggered Spare the Air days in the December. Wildfires contributed to poor air quality, but the report released Tuesday did not include data from 2017. less

Smoke from the Southern California wildfires in the Bay Area triggered Spare the Air days in the December. Wildfires contributed to poor air quality, but the report released Tuesday did not include data from ... more

A discarded mask lays among debris in the Coffey Park neighborhood in Santa Rosa. Wildfires in the North Bay resulted in “extremely high levels of particulate matter, levels that were comparable to those you might experience in Beijing,” said Jack Broadbent, chief executive officer of the Bay Area Air Quality Management District. less

A discarded mask lays among debris in the Coffey Park neighborhood in Santa Rosa. Wildfires in the North Bay resulted in “extremely high levels of particulate matter, levels that were comparable to those you ... more

California has some of the worst air quality in the nation, both in terms of ozone and particle pollution, and perhaps the biggest factor appears to be climate change, according to a new report.

The Bay Area ranked sixth worst in the nation from 2014 to 2016 in terms of short-term particle pollution in a new “State of the Air 2018” report, which the American Lung Association released Tuesday. The region ranked 13th worst in the country for ozone pollution, which scientists say is due to climate change and warming temperatures across the globe, and several Bay Area counties experienced more unhealthy ozone days than previous years.

“We are improving air quality, but the impacts of climate change are interfering with progress,” said Bonnie Holmes-Gen, senior director of air quality and climate change at the American Lung Association in California.

Poor air quality has been associated with numerous health risks, including asthma, lung cancer, and heart disease.

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The Bay Area is one of the worst regions in the country for air quality. What are the Spare the Air days that get issued so frequently? Here's an explainer.

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Though ozone pollution has generally been falling since 2000, it worsened in cities across the nation compared with the previous report.

“California retains its historic distinction with 11 of the 25 most polluted cites in that state,” the report said.

The metropolitan areas of San Jose-San Francisco, San Diego, Sacramento, Redding-Red Bluff, Chico and Los Angeles all saw more unhealthy air days on average in this report than last year’s report. In addition to the nine counties traditionally considered to make up the Bay Area, the report also included San Joaquin, Santa Cruz and San Benito counties.

The report specifically attributed increasing ozone pollution to climate change, noting that in 2016 scientists measured “the second warmest temperatures on record in the United States.”

“Ozone doesn’t come out of tailpipes or smokestacks. The more heat, the more likely ozone is to form,” said Janice Nolen, assistant vice president of national policy for the American Lung Association.

Particle pollution, meanwhile, improved in most places nationally, including San Francisco. This reflects a long-term trend: California has seen an 80 percent drop in unhealthy particle pollution days since 2004.

“Particle pollution dropped, especially for year-round averages,” Nolen said. “There were lower averages during 2014 to 2016, fewer days when it spiked, and that has to do with cleaning up major sources of pollution, replacing old dirty diesel engines, and transitioning to zero-emission vehicles.”

This drop didn’t affect every location equally, though.

San Joaquin and Santa Cruz counties both got F grades for short-term particle pollution, while San Francisco, San Mateo, Sonoma and San Benito counties all received A grades.

“The coastal parts of the San Francisco Bay Area benefit from coastal breezes, but all the pollution created by freight traffic, daily gridlock and ports is reflected inland in Alameda, Contra Costa County, near Sacramento and in San Joaquin Valley,” said Holmes-Gen.

Natural disasters such as wildfires were noted as contributing factors to poor air quality, but the report released Tuesday did not include data from 2017, when wildfires in the North Bay resulted in “extremely high levels of particulate matter, levels that were comparable to those you might experience in Beijing,” said Jack Broadbent, chief executive officer of the Bay Area Air Quality Management District.

Though that was an isolated event, Nolen warned that the historically destructive fires of last year could be a harbinger of times to come, as climate change may contribute to more extreme weather events as California also deals with drought-like conditions.

“The fires and the resulting pollution point to an ongoing theme in our national and California state of the year report,” Holmes-Gen said. “Climate change represents a significant challenge to air quality, and the public needs to understand climate impacts are happening now.”